Metal Cyano Complexes Research Articles

Ultrasensitive Monitoring of Cyanide Concentrations in Water Using a Aucore-Agshell Hybrid-Coating-Based Fiber Optical Sensor.

Cyanides, which are extremely toxic chemicals that are rapidly absorbed into the human body and interact with cytochrome oxidase, strongly inhibit cellular respiration to body death with convulsions. Cyanide ions that exist in many forms in nature such as those found in apricot kernels, cassava roots, and bamboo shoots as cyanogenic glycosides are inevitably used in various industries, including gold and silver mining as well as in dyes and plastic industries. In this study, for the sake of developing ultrahigh-sensitive sensors for cyanide monitoring in a simple manner, we chemically synthesize Aucore-Agshell hybrid nanomaterials of different core/shell thicknesses for colorimetric sensors and fiber optical sensors. Their sensing principle relies on the formation of the Ag/Au cyanocomplex upon cyanide injection. The generated metal cyanocomplex induced changes in refractive indices, causing changes in properties of localized surface plasmon resonance (LSPR), i.e., optical absorbance change for the colorimetric sensors. For fiber optical sensors, the hybrid metal nanoparticles were immobilized on the fiber core surface and the metal cyanocomplex formation induced changes in the fiber cladding refractive index, enabling quantitative cyanide detection with ultrahigh sensitivity. The LSPR-based colorimetric sensor provided the lowest detectable cyanide concentration of 5 × 10-6 M, whereas the value for the fiber-based sensor was 8 × 10-11 M.

PM oxidation over Ag-loaded perovskite-type oxide catalyst prepared by thermal decomposition of heteronuclear cyano-complex precursor

The Ag-loaded perovskite-type oxide catalysts (Ag/LaFeO3-CN and Ag/LaFeO3-imp) were prepared using two different methods, and their catalytic activities for carbon combustion were examined. Ag loading was observed to exhibit a positive effect on the catalytic activity of carbon combustion for an Ag/LaFeO3-CN catalyst that was prepared by the calcination of an Ag-loaded heteronuclear metal cyano-complex precursor. However, Ag loading was not observed to be significantly effective in case of Ag/LaFeO3-imp that was prepared by a general impregnation method. Such a noticeable enhancement in the activity of an Ag/LaFeO3-CN catalyst was assumed to originate from both the high dispersion of Ag that was loaded on LaFeO3 and from the formation of reactive oxygen species between metallic Ag species and the perovskite-type oxide.

ChemInform Abstract: Topological Motifs in Cyanometallates: From Building Units to Three‐Periodic Frameworks

AbstractReview: 314 refs.

Topological Motifs in Cyanometallates: From Building Units to Three-Periodic Frameworks.

This review focuses on topological features of three-periodic (framework) p, d, and f metal cyano complexes or cyanometallates, i.e. coordination compounds, where CN(-) ligands play the main structure-forming role. In addition, molecular, one-periodic (chain), and two-periodic (layer) cyanometallates are considered as possible building blocks of the three-periodic cyanometallates. All cyanometallates are treated as systems of nodes (mononuclear, polynuclear, or transitional metal cluster complexes) joined together via CN-containing spacers. The most typical nodes and spacers as well as methods of their connection are described and systematized. Particular attention is paid to the overall structural motifs in the three-periodic cyanometallates, especially to the relations between the local coordination (coordination figure) of structural units and the entire framework topology. The chemical factors are discussed that influence the cyanometallate topological properties due to modification of nodes, spacers, or coordination figures.

In Situ IR Studies on the Electro-Oxidation of Cyanide on Ni, Cu and Au Electrodes Electrically Polarized in Dimethyl Sulfoxide (DMSO) Electrolyte Media

Subtractively normalised Fourier transform infrared spectroscopy (SNIFTIRS) studies are reported on the electrical polarisation of nickel (Ni), copper (Cu) and gold (Au) electrodes in KCN dissolved in the polar aprotic solvent, dimethyl sulfoxide (DMSO) with tetrabutyl ammonium perchlorate (TBAP) (0.1 mol L−1) as supporting electrolyte. These studies have shown clearly that each of the metal electrodes investigated oxidised (as the applied potential was adjusted in an anodic direction) to form Ni(II), Cu(I) and Au(I)-cyano complex ions of [Ni(CN)4]2−, [Cu(CN)3]2−, [Cu(CN)2]− and [Au(CN)2]−. The distribution of other electro-oxidation products of cyanide observed, namely KOCN(s) and CO2 depended on the electrode under consideration. For Ni electrodes, DMSO-solvated CO2 and solid KOCN were observed together as the oxidation products while on Cu and Au electrodes CN− was oxidised to DMSO-solvated CO2 exclusively without any solid cyanate salt film deposition being simultaneously observed. Cu was found to be particularly electrocatalytic towards the electro-oxidation of CN− ion to CO2 with high current density values being observed. It is proposed that the metal-cyano complex ion species observed in SNIFTIRS experiments are implicated in the oxidation mechanism of CN− to KOCN and/or CO2 on these electrodes, particularly on the Cu and Au electrodes. This resembled the electrochemistry observed in similar systems involving the electrochemical oxidation of cyanide on Cu electrodes in aqueous media.

Improved catalytic activity of PrMO3 (M = Co and Fe) perovskites: synthesis of thermally stable nanoparticles by a novel hydrothermal method

A simple hydrothermal method was used to synthesize nanoperovskites using metal cyano complexes as precursors.

ChemInform Abstract: Structure and Bonding in Copper(I) Carbonyl and Cyanide Complexes

AbstractReview: 285 refs.

Structure and Bonding in Copper(I) Carbonyl and Cyanide Complexes

The coordination chemistry of copper(I) carbonyls and cyano complexes is reviewed. Primary attention is focused on structural chemistry, including coordination behavior, bridging modes, network formation, flexible coordination number, and reversible ligand binding. Additional coverage of infrared spectroscopy and orbital interactions in carbonyl and cyanide bonding and the photophysical behavior of metal cyano complexes is also included.

Transport of Au(CN)2 − by Mixtures of Amine Primene JMT and Phosphine Oxide Cyanex 923 Using the Pseudo-Emulsion Based Hollow-Fiber Strip Dispersion Technology

The transport of Au(CN)2 − between alkaline aqueous solutions and organic phases consisting of a mixture of the amine Primene JMT and the phosphine oxide Cyanex 923 in xylene was studied using the pseudo-emulsion based hollow-fiber strip dispersion (PEHFSD) technology. The feed phase was passed through the lumen side, and the pseudo-emulsions of the extractant mixtures and NaOH were passed through the shell side in a countercurrent mode using a single hollow-fiber contactor for extraction and stripping. In this membrane technology, the strippant (NaOH solution) is dispersed in the organic (Primene JMT + Cyanex 923 in xylene) membrane solution in a tank with an impeller stirrer adequate to form strip dispersion. The pseudo-emulsion phase is circulated from the reservoir tank to the membrane contactor to provide a constant supply of the organic solution to the membrane fibers. Furthermore, this technology allows a direct contact between the organic and strip solutions, providing a greater area for stripping and facilitating the metal recovery from the strip solution once both phases are separated. Various hydrodynamic and chemical parameters, such as flow of feed phase, extractant mixtures and gold concentrations, organic diluents, variation in feed pH, and the selectivity of the system with respect to the transport of different metal-cyano complexes, were investigated. Aqueous and membrane mass transfer coefficients were estimated for the present system.

Synthesis of cis- and trans-[M(CN)2(1-CH3-C6H10-NC)4] (M=Fe, Ru) and crystal structure of trans-[Ru(CN)2(1′-CH3-C6H10-NC)4

Abstract The reaction of the metal carbonyls Fe2(CO)9 or Ru3(CO)12 with 1-isocyano-1-methyl-cyclohexane produces the octahedral metal(II) cyano complexes [M(CN)2(1-CH3-C6H10-NC)4] in good yields. The cis-isomer is not isolated as a pure compound due to rearrangement processes that yield the sterically less crowded trans-isomer. The molecular structure of the trans-isomer of the ruthenium complex shows the expected almost ideal octahedral coordination of the central ruthenium ion with two cyanide and four isocyanide ligands. This reaction again indicates that isocyanides exhibiting quarternary carbon atoms in α-position with respect to the isocyano substituent in general react with di- or trinuclear metal carbonyls to yield cyano complexes with oxidized metal centres and concomitant reductive cleavage of the respective isocyanide.

A proposed mechanism for nitrate and thiocyanate elution of strong-base ion exchange resins loaded with copper and gold cyanocomplexes

The use of ion exchange resins for the recovery of gold cyanide and other base metal cyanocomplexes has been hindered by poor elution, among other factors. To overcome this drawback, saline solutions have been proposed as an eluant for the loaded cyanocomplexes, with nitrate and thiocyanate being the most promising. In the present work, the elution of gold- and copper-cyanocomplexes from polyacrylic- and polystyrene-based resins at 50 °C was studied. The results showed that copper cyanide was easily eluted from polyacrylic- and polystyrene-based ion exchange resins using either 1 mol/L SCN − or NO 3 - . However, there was poor elution of the gold cyanide complex from the polystyrene-based resins using nitrate solutions, reflecting the higher affinity that gold cyanide presents for the latter. Conversely, gold elution reached 90% using thiocyanate. Therefore, the separation of gold and copper is possible using polystyrene resins, eluting first with nitrate and then with thiocyanate. Raman spectra have shown the presence of gold and also copper complexes in the resin beads, as well as in the eluate produced during elution of both the resins, suggesting that elution takes place by an ion exchange mechanism. The better performance observed using thiocyanate, as compared to nitrate, is discussed, based on the features of both ions.

The elution of metal cyanocomplexes from polyacrylic - and polystyrene- based ion exchange resins using nitrate and thiocyanate eluants

Ion exchange resins can potentially be applied in cyanide recycling to address growing environmental concerns over the use of cyanide during gold extraction. In the present work the elution of copper-, iron-, and zinc-cyanocomplexes from polyacrylic- and polystyrene-based resins was studied. It was found that iron and copper cyanides are easily eluted from polyacrylic- and polystyrene-based ion exchange resins using either SCN- or NO3-. However, elution of the zinc cyanide complex from polystyrene-based resins was poor when using nitrate solution as eluant. Besides, an increase in elution temperature from 25 °C to 50 °C improved the elution of iron and zinc cyanides from polystyrene-based resins using a nitrate eluant; however temperature did not have any significant effect on other metal cyanocomplexes or for elution using thiocyanate. It was therefore proposed that the optimal combination of resin-eluant was site-specific, and depends on the features of the effluent, processing temperature, eluant concentration, and ion exchange resin under consideration.

Tecnologia limpa para redução de impacto ambiental do cianeto na mineração de ouro

Esse trabalho discute a aplicação de resinas de troca iônica com matriz poliacrílica para a adsorção de cianocomplexos metálicos. Ensaios em batelada mostraram que as resinas possuem elevada afinidade para os cianocomplexos de ferro e de zinco em relação aos de cobre. Já a eluição, estudada em coluna, indicou que soluções de tiocianato de sódio a 1mol/L são capazes de eluir os ciancomplexos dos três metais. Já soluções de nitrato de sódio, na mesma concentração, não são efetivas para a eluição do cianeto de zinco. Um processo de eluição seletiva é proposto onde os cianocomplexos de cobre e de ferro são eluídos com solução íons NO3-. Em seguida, o zinco é eluído com NaSCN. Ambos eluentes foram capazes de concentrar os cianocomplexos de solução, o que tem efeito benéfico nas etapas subseqüentes de regeneração do cianeto.

Utilization of the metal-cyano complex tetracyanonickelate (II) by Azotobacter vinelandii

The ability of Azotobacter vinelandii, a N(2)-fixing bacterium, to biodegrade tetracyanonickelate (TCN) was evaluated. The amounts of TCN were measured spectrophotometrically. Ammonia was determined colorimetrically by the indophenol method. The produced methane from TCN conversion by A. vinelandii was detected by gas chromatography. Results showed that A. vinelandii was able to biodegrade 1 mmol l(-1) of TCN. Ammonia and methane were detected during the process of TCN degradation. Effects of exogenous nitrogen sources on TCN degradation were addressed in this study. Results revealed that the addition of ammonia (1, 5 and 10 mmol l(-1)) into the reaction mixtures caused decrease of TCN degradation rate during a 24-h incubation period. This inhibition was also observed when nitrite (5 and 10 mmol l(-1)) was added, whereas TCN degradation still proceeded after the addition of nitrate at the same concentrations. Furthermore, the rate of TCN utilization was strikingly enhanced when 0.8% of glucose was added. Azotobacter vinelandii can degrade 1 mmol l(-1) of TCN into ammonia and methane. However, the inhibitory effects of exogenous ammonia and nitrite on TCN degradation by this bacterium were found in this study. This is the first report defining the capability of A. vinelandii to degrade TCN. This bacterium might have potential value in applied strategies for removing metal-cyano wastes. Furthermore, these findings would be helpful in designing a practical system inoculated with A. vinelandii for the treatment of TCN.

Biodegradation of the metal–cyano complex tetracyanonickelate (II) by Klebsiella oxytoca

Klebsiella oxytoca has been shown to be able to grow on 1–8 mM of tetracyanonickelate (II) [K 2Ni(CN) 4] (TCN), the sole nitrogen source. The biotransformation of 1 mM of TCN to ammonia and methane by resting cells of K. oxytoca was confirmed in this study. The utilization of 1 mM of TCN was strikingly enhanced when 0.8% of glucose was added into the phosphate buffer containing the same amount of resting cells. The growth cells under aerobic conditions had the higher capacity of degrading 1 mM of TCN than cells grown on oxygen-limiting conditions. The consumption of 1 mM of TCN by resting cells of K. oxytoca was induced when the pretreatment of these cells with 1 mM of TCN was conducted. However, the production of methane and acetylene by resting cells pretreated with ammonia (≧1 mM) was inhibited. Thus, ammonia concentrations would affect the degradation of TCN by resting cells of K. oxytoca. This might result from the suppression of nitrogenase activity of K. oxytoca by ammonia. In addition, TCN degradation did not occur in presence of nitrite. This suggests that nitrite might have the toxic effect on bacterial growth. Results from this study also show that TCN biodegradation by cell-free extracts was not observed. This might be due to the oxygen exposure, which caused the inactivation of nitrogenase (oxygen-labile enzyme).

Transport of Au(CN) 2− across a supported liquid membrane using mixtures of amine Primene JMT and phosphine oxide Cyanex 923

The transport of Au(CN) 2 − between aqueous solutions and organic phases of the mixture of the amine Primene JMT and the phosphine oxide Cyanex 923 in xylene was studied under various experimental conditions, i.e., extractant mixtures and gold concentrations. The behaviour of the system with different organic diluents, aqueous ionic strength and the selectivity of the system with respect to the transport of different metal–cyano complexes were also investigated. The transport of gold(I) can be ascribed to a mechanism which consists of (i) a diffusion process through the feed aqueous diffusion layer, (ii) a fast interfacial chemical reaction and (iii) a diffusion of HAu(CN) 2RL and HAu(CN) 2RL 2 (R=the amine, L=the phosphine oxide) through the membrane.

Solvent extraction of silver by LIX® 79: experimental equilibrium study

The extraction of silver(I) from argentocyanide aqueous cyanide solutions using LIX® 79 has been studied. Different variables that could affect the extraction system were evaluated: equilibration time, aqueous pH, metal and extractant concentrations, and organic phase diluent. The extraction of the Ag(CN)2− complex with respect to other metal-cyano complexes has also been studied on both synthetic and real leach solutions. Experimental data relating to silver have been analysed numerically to determine the stoichiometry of the extracted species and its equilibrium constant. It was found that silver(I) was extracted into the organic phase by the formation of the species RHAg(CN)2 (LIX 79 = R). Copyright © 2004 Society of Chemical Industry

Cyanide regeneration by AVR process using ion exchange polymeric resins

This work presents laboratory bench scale results for cyanide regeneration from pure alkaline aqueous solutions of gold, copper and iron cyanocomplexes using an innovative option of the AVR process associated to the ion exchange polymeric resins Imac HP555s ® ((Room&Haas––USA) and Amberlite IRA-420 ® (Room&Haas Brasil Ltda.) in columns. The resin Imac HP555s ® adsorbed 64.5% CN from the alkaline solution containing metal cyanocomplexes. Meanwhile, the elution stage with H 2SO 4 and thiourea reached 31.2% CN, 86.2% Au, 86.4% Cu and 41.5% Fe. The resin IRA-420 ® adsorbed 53.4% CN under the same experimental conditions adopted for the resin Imac HP555s ®. The resin Amberlite IRA-420 ® eluted 48% CN, 96.8% Au, 9.1% Cu and 76% Fe.

Facilitated transport of Au(CN)<sub>2</sub> and other metal-cyanide complexes using amines

The use of different amines, Hostarex A327 (tertiary), Amberlite LA2 (secondary) and Primene JMT (primary), as carriers in the facilitated supported liquid membrane transport of metal-cyanide complexes, with special attention to gold, along with the addition of neutral organophosphorous derivatives (Lewis bases) to the amine organic phase as synergistic agents for the transport of Au(CN) 2 , at alkaline pH values and selectively against other metal-cyano complexes, is investigated.

The phosphine oxides Cyanex 921 and Cyanex 923 as carriers for facilitated transport of gold(I) cyanide aqueous solutions

The behaviour of the phosphine oxides Cyanex 921 and Cyanex 923 in the facilitated transport of gold(I) from cyanide solutions is described. Transport is studied as a function of several variables such as stirring speeds of the aqueous phases, membrane phase diluent, pH of the source phase, ionic strength, and gold and carrier concentrations. The separation of the gold(I) cyanide complex from other metal-cyano complexes present in the source phase as well as the behaviour of phosphine oxides with respect to other neutral organophosphorous derivatives (tri- n-butylphosphate (TBP) and dibutyl butylphosphonate (DBBP)) are also investigated.